Electroplating



Patented Oct. 1, 1940 UNITED STATES PATENT OFFICE ELEUIROPLATHVG York NoDrawing. Application March 30, 1938,

Serial No. 198,826

2 Claims.

Our invention relates generally to electroplating and more particularly,to a novel electroplating bath.

One of the objects of our invention is to provide a novel electroplatingbath of the character described which is adapted to electrodeposit anovel and highly improved alloy plate.

Another object of our invention is to provide a novel electroplatingbath of the character described which is adapted to electrodeposit anovel and highly improved alloy plate upon zinc die cast objects andwhich is at the same time highly resistant to corrosion.

A .further object of our invention is to provide an electroplating bathwhich will deposit a copper-cobalt-tin alloy plate of the characterdescribed with consistently satisfactory results and in a simple andinexpensive manner.

Other objects of our invention will in part be obvious and in parthereinafter pointed out.

In accordance with our invention, a dry composition, that is, anelectroplating bath composition, may be prepared by making a mixture ofcopper salts, cobalt salts, tin salts and an alkaline cyanide. Thiscomposition is added to water or any other suitable solvent to form anelectroplating bath solution from which may be electrodeposited upon anobject. in a manner and by means well known in the art, an alloy platecomprising copper, cobalt and tin.

We have found that when an electroplating bath solution, prepared inaccordance with our invention, contains a copper content of from about0.04 to 15.85 grams per gallon, a cobalt content of from about 0.02 to9.2 grams per galion, and a tin content of from about 0.02 to 3.6 gramsper gallon, a satisfactory copper-cobalttin alloy plate may beelectrodeposited therefrom. It is understood, however, that ourinvention is notto be construed as being limited by these ranges.

In supplying the copper, cobalt and tin contents of the bath, any saltor salts of copper, cobalt and tin may be employed in the dry platingcomposition which, when combined with other ingredients comprising. theplating composition, will dissolve in the solvent employed. Some ofthese salts are:

Sodium stannate NazSnOa 3H2O Stannous phosphate Sn3(PO4) 2 Stannoustartrate SnC4H4Oe Copper cyanide Cu2(CN) 2 Copper sulphate CuSO;

Copper tartrate CuC4H4Os Cobaltous sulfate CoSO4-7H2O Cobalt tartrateCoC4H40s Cobalt carbonate CoCOs Cobalt cyanide Co (CN) 2 2H2O Sodiumcobaltocyanide Na4Co (CN) 15 Cobalt phosphate Coa(PO4) 2 5 Suftlcientalkaline cyanide should be mixed into the dry bath composition to ensurea free or uncombined alkaline cyanide content in the electroplating bathof from 0.3 ounce to 6 ounces per gallon. We have found that the 10 mostsatisfactory results are obtained by the presence of 2 to 3 ounces offree alkaline cyanide per gallon.

In connection with the practice of our invention, suitable platingvoltages, temperatures and current densities generally known to the artmay be employed.

By our invention, saltsof copper, cobalt and tin may be satisfactorilyused to electrodeposit a bright plate from an alkaline cyanideelectroplating bath for periods of time up to one minute, without thenecessity of employing any addition salts for brightening orconductivity. The electroplate thus obtained suflices for an inexpensiveand practical plate on articles such as those used in the novelty trade.

When a heavier and more durable plate is desired, we have found thataddition agents as brighteners and for conductivity, such as thoselisted below, may be used. 80

Tri-sodium phosphate NaaPOrHaO Rochelle salt NaKC4H406 4H2O Potassiumthiocyanate KCNS Sodium bisulfite N aHSOs Sodium sulfate NazSOr Sodiumcarbonate NazCOa Sodium arsenite NaAsOz Di-sodium phosphate NacHPO4Sodium pyrophosphate Na4P2O'1-10H2O Arsenious acid AszO:

Sodium phenylate (phenate) NaCcHsO Goulac (tailings from sulphite liquorconcentrate in preparation of wood pulp) Sodium thiosulfate NazSaOs Sodaalum Na-A1'(SO4)2-12HzO 5 Glucose CeHmOs Dextrose CsHmOa Dextrine(Col-1100s) x Ammonium molybdate (NH4) 6MO7024'4H2O Sodium oxalateNazCzOr Ammonium hydroxide NHQOH Bone glue Thiourea NI-Iz-CS-NI-IzPotassium ferrocyanide K;Fe(CN)s The above-listed addition salts arerepresenu tative members of their groups. For example, Rochelle salt isa. member of the tartrate group and merely given as an example of such.Other tartrates, such as ammonium, copper, magnesium, cobalt or tintartrate, would cause the plating bath to function equally well.

We have found that satisfactory results are obtained by using .thefollowing addition. salts for brightening or conductivity either singly,doubly, or in multiple combination in the ranges set forth.

Addition mum gf g Eggfig I Gram 6 1m 1 at Twat" Tri-Bodium phosphate0.01to 28. flodiumarsenitemn 0.01to 1 0. 0.01m 1 0.

333% W-Ira."- 8'81 1 1 3' "Go lTc up a 0101 1:8 1 01 0.01:0 1 0.

0.01 to 1 o.

0.01 to 1 o.

0.01 to 1 o.

0.01 to so 14.

0c. 1101: C r Hon Ammonium hydroxide H. 30 6 pc We have found that thedouble combinations of addition agents listed below also give goodresults:

(Grams per gallon) 0.01 Di sodium phos- +1.0 Rochelle salt 1.0 Bone glue1.0 Bone glue 1.0 Bone glue 1.0 Bone glue +0.01 Sodium bisulfite +0.05Sodium sulfate +0.05 Soda alum +1.0 Glucose The following are specificexamples of dry bath compositions which we have found to give goodresults, it being understood that they are in no way limltative. Theweights given are for use with one gallon of a plating bath.

Example I Grams Sodium stannate 8.60 Sodium cyanide 90.00 Copper cyanide18.00 Cobalt carbonate 5.80

Emails I! Sodium stannate 8.60 Sodium cyanide 90.00 Copper cyanide--.18.00 Cobalt carbonate 5.80 Rochelle sal 1.25

123.65 Example III Grams Sodium stannate 8.60 Sodium cy 90.00 Coppercyanide 18.00 Cobalt carbonate; 5.80 Rochelle salt 1.25 Tri-sodiumphosphate 7.60

131.25 Example IV Rochelle salt 1.25 Sodium stannate 8.60 Tri-sodiumphosphate 7.60 Sodium cy 90.00 Copper cyanide 18.00 Cobaltous sulfate13.80

We have found that by our invention a ferrocyanide, such as potassiumferrocyanide, may be used to partially replace sodium cyanide in thebath and reduce the effect of carbonate formation from the breakdown ofsodium cyanide as is illustrated by the following example:

Grams Cuban cyanide 5.40 Sodium cy L 50.00

Copper cyanide 18.00 Sodium stannate 8.60

82.00 Potassium ferrocyanide 1 to 10 grams.

By our invention, as above described, we have been able to produce anelectroplated alloy, characterized by its whiteness which approachessilver, has a high reflectivity, and is at the same time hard andductile so that metals upon which our alloy has been electrodepositedmay be formed without peeling, chipping or cracking. Also, our alloyplate forms a substantially uniform deposit on irregular surfaces due tothe high throwing power of the solution. Also, it is highlytarnish-resistant, being unaffected by salt spray, mustard and olives,lemon juice, or the like. The alloy plate is moreover resistant tocorrosion by cold caustic or alkaline solutions of any strength and canonly be slowly dissolved by any single acid, so that it furnishes a goodfoundation or primary plate because other plates, such as a chromiumplate or a nickel plate, may be readily stripped therefrom withoutaffecting it. This latter characteristic of the alloy plate produced byour invention, namely its excellence as a primary plate, is particularlyimportant in regard to zinc die cast objects on which primaryelectroplates have heretofore tended to be absorbed or become blistered,or on which difliculty has been experienced in electrodepositing asecond plate. We have found that our novel bath will electrodeposit asmooth plate on zinc die cast objects which will not be absorbed and maybe used as a base plate for other electrodeposits having any speciallydesired characteristics.

It will thus be seen that'there is provided a composition, bath andprocess by means of which the several objects of this invention areachieved, and which are well adapted to meet the conditions of Practicaluse.

As various possible embodiments might be made of the above invention,and as various changes might be made in the embodiments above set forth,it is to be understood that all matter herein set forth is to beinterpreted as illustrative and not in a limiting sense.

Having thus described our invention, we claim as new and desire tosecure by Letters Patent:

1. A process of electrodepositing a white copper-cobalt-tin alloy platecomprising passing current through an aqueous alkali cyanide bathsolution containing copper salts, cobalt salts and tin salts, thequantities of said salts. being such that the metallic contents of onegallon of said solution will be from about 0.04 to 15.85 grams ofcopper, from about 0.02 to 9.2 grams of cobalt, and from about 0.02 to3.6 grams of tin, and having a free alkali cyanide content of from 0.3to 6 ounces per gallon of solution.

2. An electroplating bath for depositing a white alloy plate of copper,cobalt and tin, said bath comprising an aqueous alkali cyanide solutionof copper, cobalt and tin salts and from 0.3 to 6 ounces of free alkalicyanide per gallon of solution, said bath having metallic contents pergallon of solution of from about 0.04 to 15.85 grams of copper, fromabout 0.02 to 9.2 grams of cobalt and from about 0.02 to 3.6 grams oftin.

1 LIONEL CINAMON.

SAMUEL SKLAREW.

